1. Field of the Invention
This invention relates to the preparation of an alcohol-free alkali or alkaline earth metal alcoholate. More particularly, this invention relates to the preparation of an alcohol-free alkaline or alkaline earth metal alcoholate dissolved in an inert solvent. This invention particularly relates to the preparation of such a composition wherein the alkali or alkaline earth metal alcoholate is present in the inert solvent at a high purity.
2. Discussion of the Prior Art
It is known to prepare metal alcoholates from free metals and monovalent alcohols. Depending upon the extent to which the metals employed are divided, the reaction proceeds more or less violently, particularly when using potassium or sodium. The reaction is less violent the longer the chain length of the alcohol is. Primary alcohols react the fastest, the tertiary alcohols reacting the slowest. It is also known to decrease the reaction rate by use of diluents such as, for instance, ether and benzene. (Houben-Weyl VI/2 (1963), page 7). The alkali metal alcoholates prepared in this manner frequently contain 1 to 3 mols of crystal alcohol. Crystal alcohol refers to alcohol molecules in a crystal structure. The crystal alcohols can be removed from the alkali metal alcoholates by heating the composition in hydrogen or in a nitrogen stream or by azeotropic distillation.
It is also known to prepare sodium ethylate free from crystal alcohol by use of a sodium wire which is covered by a small layer of ether. The wire is contacted with the calculated amount of absolute alcohol which is added dropwise to the wire. After about 24 hours the development of hydrogen is terminated. Potassium ethylate can be prepared in the same manner.
It is also known to prepare alkali metal alcoholates free from crystal alcohol by first finely dividing the alkali metal and disposing the same in boiling xylene by means of vigorous stirring. The reaction mixture is thereafter cooled and to the same there is added, drop by drop, the calculated amount of alcohol which is mixed with twice the volume of xylene. The reaction mixture is stirred. This reaction is carried out in a thick-walled vessel, equipped with an agitator, reflux condenser and dropping funnel. The reaction heat produced by the reaction must be removed continuously in order to prevent the reaction from running away. (Houben-Weyl VI/2 (1963), page 8).
These known processes are difficult to control, in particular when they are performed on an industrial scale. Another disadvantage resides in the fact that the metal which is used must initially be ground into a finely divided state. This obviously requires an additional processing step.
In this manner it is possible to prepare alcoholates of a number of primary, lower or higher monovalent alcohols in a crystal alcohol-free state, e.g., of methyl, ethyl, n-propyl alcohol or butanol-(1). However, by this method it has thus far not been possible to prepare alcoholates from reaction of iso-alcohols or carbinols, secondary or tertiary lower or higher alcohols, e.g., isopropyl alcohol, butanol-(2), 2-methyl propanol-(1), 2-methyl-propanol-(2), or the isomeric amyl alcohols, such as pentanol-(2), pentanol-(3), 2-methyl-butanol-(3), 2-methyl butanol-(2), 2-methyl-butanol-(1), 2,2-dimethyl propanol-(1) on an industrial scale with an economically reasonable reaction time and without excessive additional processing steps.
It is also known to prepare potassium tertiary butylate by contacting potassium dust with excessive amounts of tertiary butyl alcohol over a reaction period of about 8 hours with subsequent distillation of the alcohol. However, in this process a product containing crystal alcohol results (cf. Houben-Weyl VI/2 (1963), page 9). In order to remove the crystal alcohol, the dry residue is heated in an oil bath to 200.degree.-220.degree. C. An alcohol free potassium tertiary butylate is obtained in the form of a white granular-crystalline sublimate.
Thus far, it has not been possible to prepare, in direct synthesis, an alcohol-free alkali or alkaline earth metal alcoholate dissolved in a hydrocarbon or hydrocarbon mixture. For instance, it has not thus far been possible to obtain, in direct synthesis, a hydrocarbonaceous mixture containing an alkali or alkaline earth metal alcoholate of an iso-alcohol, carbinol, secondary or tertiary alcohol. In order to prepare such solutions it has thus far been necessary to first free an alcohol-containing alcoholate prepared by the above described methods or an alcohol-containing alcoholate by re-alcoholizing an alkali metal alcoholate of a lower primary alcohol with a higher iso-alcohol, carbinol, secondary alcohol or tertiary alcohol from crystal alcohol by thermal treatment. This thermal treatment is then followed by dissolving the now alcohol-free alcoholate in the inert solvent.
Alkali and alkaline earth metal alcoholates are known to be of substantial use in the chemical industry. Especially the pure crystal alcohol-free alkali or alkaline earth metal tertiary butylate is used increasingly more as a condensation agent. The reason for this is due to the fact that the tertiary butylate anion is an especially strong proton acceptor and the released sterically hindered tertiary butyl alcohol does not in most instances cause any side reactions.
Owing to the increased handling safety and accurate reaction controls, it has become advantageous to use alcohol-free alkali and alkaline earth metal alcoholates dissolved in inert solvents.
It is, therefore, an object of the present invention to provide a process by which an alcohol-free alkali and alkaline earth metal alcoholate dissolved in inert solvents can be prepared which process can be performed by a direct process without involving the initial preparation of an alcohol-containing alkali or alkaline earth metal alcoholate followed by separation of the alcohol therefrom and a dissolution of the alcohol-free alcoholate in inert solvent.
It is therefore an object of the present invention to provide such a direct process which characterize the heretofore known processes unencumbered by the disadvantages.